This 2012 McGill University rodent study found:

“Variations in maternal care in the rat affect hippocampal morphology and function as well as performance on hippocampal-dependent tests of learning and memory in the offspring.

Thus, in the rat, as in humans, social influences operate during early life to influence the structure and function of brain regions critical for cognitive capacity.

Variations in maternal care can influence hippocampal function and cognitive performance through the epigenetic regulation of genes.”

http://www.pnas.org/content/109/Supplement_2/17200.full “Variations in postnatal maternal care and the epigenetic regulation of metabotropic glutamate receptor 1 expression and hippocampal function in the rat”